First crack at help text

src/std.rs

@@ -5,17 +5,47 @@
 
 extern crate std;
 
-use crate::{HandlerResult, Opt, Opts, ParseControl, ParseResult};
+use std::{env, eprintln, println};
+use std::path::Path;
+use crate::{HandlerResult, Opt, Opts, ParseControl, ParseResult, StandardShortUsageWriter, HelpWriterContext, StandardFullHelpWriter, HelpWriter};
 
 impl<ID: 'static> Opts<ID> {
-  /// Wrapper around `parse` that gathers arguments from the command line and prints errors to stderr.
+  /// Wrapper around `jaarg::parse` that gathers arguments from the command line and prints errors to stderr.
+  /// The errors are formatted in a standard user-friendly format.
   ///
-  /// Requires std
-  pub fn parse_env<'a>(&self, handler: impl FnMut(&ID, &Opt<ID>, &str, &str) -> HandlerResult<'a, ParseControl>
+  /// Requires features = [std]
+  pub fn parse_easy<'a>(&self, handler: impl FnMut(&str, &ID, &Opt<ID>, &str, &str) -> HandlerResult<'a, ParseControl>
   ) -> ParseResult {
-    let mut argv = std::env::args();
+    let mut argv = env::args();
     let argv0 = argv.next().unwrap();
-    let program_name = std::path::Path::new(&argv0).file_name().unwrap().to_string_lossy();
-    self.parse(&program_name, argv, handler, |e| { std::eprintln!("error: {e}") })
+    let program_name = Path::new(&argv0).file_name().unwrap().to_string_lossy();
+    self.parse(&program_name, argv, handler, |program_name, e| {
+      eprintln!("{program_name}: {e}");
+      self.eprint_help::<StandardShortUsageWriter<'_, ID>>(program_name);
+      eprintln!("Run '{program_name} --help' to view all available options.");
+    })
+  }
+
+  /// Prints full help text for the options using the standard full
+  ///
+  /// Requires features = [std]
+  pub fn print_full_help(&self, program_name: &str) {
+    self.print_help::<StandardFullHelpWriter<'_, ID>>(program_name);
+  }
+
+  /// Print help text to stdout using the provided help writer
+  ///
+  /// Requires features = [std]
+  pub fn print_help<'a, W: HelpWriter<'a, ID>>(&'a self, program_name: &'a str) {
+    let ctx = HelpWriterContext { options: self, program_name };
+    println!("{}", W::new(ctx));
+  }
+
+  /// Print help text to stderr using the provided help writer
+  ///
+  /// Requires features = [std]
+  pub fn eprint_help<'a, W: HelpWriter<'a, ID>>(&'a self, program_name: &'a str) {
+    let ctx = HelpWriterContext { options: self, program_name };
+    eprintln!("{}", W::new(ctx));
   }
 }